1. Field of the Invention
The present invention relates to a method and a structure for waterproofing a terminal splice, and in particular for waterproofing the terminal splice at a location where strands stripped from a plurality of wire terminals are connected.
2. Description of Related Art
A conventional method to electrically connect wires of a wire harness routed in an automobile is, as shown in FIG. 6, to weld and join strands Wa stripped from a plurality of wire W terminals to form a terminal splice Y. Waterproofing is required when terminal splice Y is placed in an area exposed to water as the wire harness is installed in a vehicle. FIG. 6 illustrates a conventional waterproofing method. In the conventional method, a specified amount of waterproofing agent 2 is injected into cap 1 from an injector (not shown in the figure) and terminal splice Y of each wire W is inserted into cap 1. Then, waterproofing agent 2 is hardened to seal terminal splice Y.
Injecting waterproofing agent 2 into cap 1, however, requires a certain internal diameter of cap 1 due to the injector's capability. Moreover, an external diameter of the cap is large compared to the size of terminal splice Y since cap 1 needs to be able to accommodate various sizes of terminal splices Y due to a large difference in their specifications. Since cap 1 used is large even if terminal splice Y is small, the cap occupies a space when terminal splice Y is placed in an external part, reducing space efficiency. Especially, when terminal splice Y is placed into a corrugated tube, a large-diameter corrugated tube is required, resulting in cost increase. In addition, the larger the internal diameter of cap 1 becomes, the more waterproofing agent 2 is required for the injection, which increases the cost of waterproofing agent 2.
Japanese Patent Laid-open Publication Hei 10-108345 provides a waterproofing method that tight-seals wire connection 3 as shown in FIG. 7. In the method, wire connection 3 having crimped part 3a, where a plurality of wire W strands are connected, is covered with heat shrinkable tube 4 having one end sealed by hot-melt 5. Butyl rubber 6 is injected inside heat shrinkable tube 4, which is then heat-treated to shrink the tube and to lower viscosity of butyl rubber 6 and spread the substance. Using butyl rubber 6 of low fluidity as filler, however, reduces workability when injecting butyl rubber 6 inside heat shrinkable tube 4. Moreover, waterproof performance may decline when butyl rubber 6 does not fill every gap between wires W and with heat shrinkable tube 4, depending on the location of butyl rubber 6 in heat shrinkable tube 4 or the heat level.